But some emerged from the devastation. Struggling with survivors’ guilt and sick with illnesses caused by the radiation, they were shunned for years as living reminders of the human capacity to engineer horror.

On Friday, Nihon Hidankyo, a collective of Japanese atomic bomb survivors, was awarded the 2024 Nobel Peace Prize for its decades-long campaign to rid the world of nuclear weapons.

The group was honored by the Norwegian Nobel Committee for “demonstrating through witness testimony that nuclear weapons must never be used again.”

The survivors of the bombings — more than 100,000 are still living — “help us to describe the indescribable, to think the unthinkable, and to somehow grasp the incomprehensible pain and suffering caused by nuclear weapons,” Jorgen Watne Frydnes, the committee chairman, said.

The Nobel committee noted that although nuclear weapons have not been used since the Japanese cities were attacked by American bombers in August 1945, nuclear powers are modernizing their arsenals and other countries are trying to join the nuclear club.

The committee did not name any specific nations. But President Vladimir V. Putin of Russia has threatened to use tactical nuclear weapons in Ukraine. And concerns are growing about nuclear proliferation in the Middle East and Asia.

“At this moment in human history, it is worth reminding ourselves that nuclear weapons are the most destructive weapons the world has ever seen,” the committee said.

Other Nobel laureates have been awarded the Peace Prize for their campaigns against nuclear weapons, including the chemist turned activist Linus Pauling in 1962 and the International Atomic Energy Agency in 2005.

It was nearly 80 years ago, on Aug. 6 and 9, 1945, that American B-29 bombers dropped two atomic weapons, code named Little Boy and Fat Man, on Hiroshima and Nagasaki. The Nobel committee said that about 120,000 people were killed by the detonations. A similar number died from burns, injuries and radiation-induced diseases in the months and years that followed.

That first and only use of nuclear weapons was followed by the end of World War II, but also by a nuclear weapons arms race. In the deserts of China and Algeria and on the atolls of the South Pacific, nuclear powers tested increasingly more powerful weapons that spewed harmful radiation.

Today, nine countries are considered nuclear powers: the United States, Russia, France, China, Britain, Pakistan, India, Israel and North Korea. There are nearly 13,000 weapons in the global nuclear stockpile, according to the Union of Concerned Scientists.

In Japan, the payloads dropped on Hiroshima and Nagasaki echoed far beyond the ruined cities. A once martial Japan blossomed into a culture that has dedicated itself, even in its Constitution, to peace. Japanese children flashed peace signs for photos and Olympic ceremonies in Japan featured white doves. But many Japanese felt more comfortable averting their gaze from the hibakusha, or “the people affected by bombs,” as the Hiroshima and Nagasaki survivors are known.

For many in Japan — and in the United States — the hibakusha represented something that they didn’t want to see. When Terumi Tanaka, a representative of Nihon Hidankyo, visited the United Nations in 1976, he was shocked to discover that, at the time, the ruination caused by the atomic bombs was not that well known. The United Nations had drastically downplayed the death toll.

Some Japanese feared that radiation-induced diseases were contagious, and hibakusha worried about their marriage and career prospects. Sunao Tsuboi, the onetime chairman of Nihon Hidankyo who was less than a mile from the center of the Hiroshima blast when it went off, recalled that he and his fiancée took sleeping pills in a suicide pact after being told by her parents that they could not wed because he was a hibakusha. (They survived and married, and Mr. Tsuboi met President Barack Obama when he visited Hiroshima in 2016.)

“Starting with the inhumane acts of Hiroshima and Nagasaki, we were oppressed by the United States and abandoned by the Japanese government for a long time,” Sueichi Kido, the secretary general of Nihon Hidankyo and a survivor of the Nagasaki bomb, told NHK, the Japanese broadcaster, on Friday.

When Nihon Hidankyo formed in 1956, its founding declaration described the stigma of outliving nuclear annihilation. “We have survived until now in silence, with our heads down,” the statement said.

In the years after the war, the hibakusha were living evidence of the fact that the United States, which occupied Japan after World War II and imposed upon the nation a Constitution that renounced war, had caused the destruction of Hiroshima and Nagasaki.

The hibakusha were also a counternarrative to a Japan that was developing into a high-tech economic giant fueled, in some cases, by nuclear power. The 2011 earthquake and tsunami, which led to a meltdown at a nuclear power plant in Fukushima, once again forced a national moment of reflection. Since the nuclear accident, most of Japan’s nuclear reactors remain shuttered.

These days, the hibakusha, whose largest grouping is Nihon Hidankyo, are celebrated for their continued campaign against nuclear weapons despite the obstacles. Many have dedicated their lives to recounting their stories of loss and pain, in an effort to ensure that the world comprehends the profound terror that a nuclear war could bring.

The Nobel committee said that such witness accounts “have contributed greatly to the establishment of a nuclear taboo.”

But that taboo, said Mr. Frydnes, the Nobel committee chairman, “is under pressure.”

Henrik Urdal, the director of the Peace Research Institute Oslo, said in a statement that threats by both longtime nuclear powers and by newer actors show the crucial timing of the prize awarded to Nihon Hidankyo.

“In an era where automated weapon systems and A.I.-driven warfare are emerging, their call for disarmament is not just historical, it is a critical message for our future,” Mr. Urdal said.

In awarding the peace prize to Nihon Hidankyo, the Nobel committee said that even though the hibakusha are growing old, a new generation of Japanese could campaign for nuclear disarmament.

But Japan’s neighbors include Russia and China.

From Laos, where he was attending a regional summit, Prime Minister Shigeru Ishiba of Japan said that it was “extremely significant” that Nihon Hidankyo was awarded the Nobel Peace Prize.

Mr. Ishiba, who was previously the country’s defense minister, has called for Japan to adopt a more muscular military stance. He supports revising Japan’s Constitution to add a specific mention of Japan’s military, which is called the Japan Self-Defense Forces. The United States is treaty-bound to defend Japan if it comes under attack, and Mr. Ishiba, before he became prime minister, suggested that the United States could possibly share its nuclear weapons with Asia.

And while the Japanese public still overwhelmingly supports nuclear disarmament, some young people have expressed support for the nuclear deterrence theory, in which countries arm themselves to deter attack, a Nihon Hidankyo member told the Asahi Shimbun, a Japanese newspaper.

Last year, at a summit in Hiroshima, the Group of 7 nations released a statement that did not call outright for nuclear disarmament, instead urging that nuclear weapons “for as long as they exist, should serve defensive purposes, deter aggression and prevent war and coercion.”

But Toshiyuki Mimaki, the chairman of Nihon Hidankyo, said on Friday that his foremost wish was for the world to “please abolish nuclear weapons while we are alive.”

Mr. Mimaki is 82.

Reporting was contributed by Megan Specia, Steven Erlanger, Anton Troianovski, John Yoon and Lynsey Chutel.

The payloads dropped by American B-29 bombers on the Japanese cities of Hiroshima and Nagasaki in August 1945 echoed far beyond the ruined cities and catalyzed vertiginous contradictions: The bombs, code-named Little Boy and Fat Man, were followed by the end of World War II, but also by an arms race that has made nine countries into nuclear powers, according to the Union of Concerned Scientists.

In the wake of the atomic blasts, a once martial Japan blossomed into a culture that has dedicated itself, even in its Constitution, to peace. Japanese children flashed peace signs for photos, and Olympic ceremonies in Japan featured white doves. But many Japanese feel more comfortable averting their gaze from the more than 100,000 remaining Hibakusha, as the Hiroshima and Nagasaki survivors are known.

Struggling with both survivor’s guilt and radiation-induced illnesses, the Hibakusha knew they represented something that many in Japan — and the victorious United States — didn’t want to see.

Some Japanese feared that radiation-induced diseases were contagious, and Hibakusha worried about their marriage and career prospects.

“Starting with the inhumane acts of Hiroshima and Nagasaki, we were oppressed by the United States and abandoned by the Japanese government for a long time,” Sueichi Kido, the secretary general of Nihon Hidankyo and a survivor of the Nagasaki bomb, told NHK, the Japanese broadcaster, on Friday.

These days, the Hibakusha, whose largest collective is Nihon Hidankyo, are celebrated for their continued campaign against nuclear weapons despite the obstacles. Many have dedicated their lives to recounting their stories of loss and pain in an effort to ensure that the world comprehends the profound devastation a nuclear war could bring.

It is that crusade for which Nihon Hidankyo was awarded the Nobel Peace Prize on Friday.

The miseries of the Hibakusha, said Jorgen Watne Frydnes, the chairman of the Norwegian Nobel Committee, “help us to describe the indescribable, to think the unthinkable, and to somehow grasp the incomprehensible pain and suffering caused by nuclear weapons.”

When Hidankyo formed in 1956, its founding declaration described the hardship of existing as living memorials to nuclear devastation. “We have survived until now in silence, with our heads down,” the statement said.

In the years after the war, the Hibakusha, whose name means “people affected by bombs,” were a tangible reminder that the United States, which occupied Japan after World War II and imposed upon the nation a war-renouncing Constitution, had caused the ruination of Hiroshima and Nagasaki.

The Hibakusha were also a counternarrative to a Japan that was developing into a high-tech economic giant fueled, in some cases, by nuclear power. The 2011 earthquake and tsunami, which led to a meltdown at a nuclear power plant in Fukushima, once again forced a national moment of reflection. Most of Japan’s 54 nuclear reactors remain shuttered.

In awarding the Nobel Peace Prize to Nihon Hidankyo, the Nobel committee said that even though the Hibakusha are growing old, a new generation of Japanese is “helping to maintain the nuclear taboo — a precondition of a peaceful future for humanity.”

But Japan’s near neighbors are Russia and China. And, as the Nobel committee pointed out, nuclear arsenals are growing and nuclear threats are proliferating worldwide.

From Laos, where he was attending a regional summit, Prime Minister Shigeru Ishiba of Japan said that it was “extremely significant” that Nihon Hidankyo was awarded the Nobel Peace Prize.

Mr. Ishiba, who was previously defense minister, has called for Japan to adopt a more muscular military stance. He supports revising Japan’s Constitution to add a specific mention of Japan’s military, which is called the Self-Defense Forces. While the United States is treaty-bound to defend Japan if it comes under attack, Mr. Ishiba has said that he wants Japan to be equals with the United States in terms of security.

And while the Japanese public still overwhelmingly supports nuclear disarmament, some young people have expressed support for the nuclear deterrence theory, in which countries arm themselves to deter attack, a Hidankyo member told the Asahi Shimbun, a Japanese newspaper, last year.

Last year, at a summit in Hiroshima, the Group of 7 nations released a statement that did not call outright for nuclear disarmament, instead urging that nuclear weapons “for as long as they exist, should serve defensive purposes, deter aggression and prevent war and coercion.”

Toshiyuki Mimaki, the chairman of Nihon Hidankyo, said on Friday that his foremost wish was for the world to “please abolish nuclear weapons while we are alive.”

Other survivors of the Hiroshima and Nagasaki attacks by the United States reacted to the news of the Peace Prize with a mix of surprise, bittersweet joy and renewed determination in their mission, which has grown ever more urgent as the number of living witnesses to the bombings has dwindled.

Many have dedicated their lives to sharing their experiences and to campaigning for nuclear disarmament.

As the announcement that Nihon Hidankyo had received the Nobel was broadcast in the rooms of Hiroshima’s City Hall on Friday, decades of campaigning culminated in tears for the survivors and their descendants, who are known as “hibakusha,” or “bomb-affected people,” in Japan.

“Please abolish nuclear weapons while we are alive,” Mr. Mimaki told reporters at a news conference in which he wept openly. “That is the wish of 114,000 hibakusha.”

The words hibakusha and nuclear weapons were repeated several times in the Peace Prize announcement that was broadcast worldwide from the Norwegian Nobel Institute in Oslo, bringing the survivors’ concerns to a global audience as the bombings’ 80th anniversary approaches.

“There is no greater encouragement for us atomic bomb survivors,” Takeshi Yamakawa, 88, told NHK, Japan’s public broadcaster.

The award also prompted survivors to voice their concerns that global tensions, including the wars in Ukraine and the Gaza Strip, could escalate into nuclear war. For some survivors of the bombs, the prize resurfaced the horrific pain that followed the American nuclear attacks on Japan.

“Starting with the inhumane acts of Hiroshima and Nagasaki, we were oppressed by the United States and abandoned by the Japanese government for a long time,” said Sueichi Kido, the secretary general of Nihon Hidankyo, who was exposed to the bomb in Nagasaki when he was 5.

The recognition also resonated with younger people. Yuuka Ohara, 17, a third-generation hibakusha from Nagasaki, said she was happy that more people would learn about the mission to abolish nuclear weapons.

“It’s our generation’s mission to succeed them,” she said.

“This year’s prize joins a distinguished list of Peace Prizes that the committee has previously awarded to champions of nuclear disarmament and arms control,” he said.

Here’s a look at previous laureates who campaigned for nuclear disarmament:

Linus Pauling: The chemist turned activist spoke out against the nuclear arms race after the Hiroshima and Nagasaki bombings. He was awarded the Peace Prize in 1962, eight years after receiving the Nobel in Chemistry.

Eisaku Sato: During his tenure as Japan’s prime minister, Mr. Sato was awarded the 1974 Peace Prize, in part for having signed the 1970 nonproliferation treaty to limit the use of nuclear weapons.

Alva Myrdal and Alfonso García: Ms. Myrdal, a Swedish lawmaker who campaigned for disarmament, and Mr. García, a Mexican diplomat, shared the 1982 award. Mr. García led an effort to make Latin America a nuclear-free zone in the wake of the 1962 Cuban missile crisis.

International Physicians for the Prevention of Nuclear War: This global organization, which represents doctors, medical students and other concerned citizens in more than 50 countries, received the 1985 Nobel Peace Prize for spreading awareness about the consequences of using nuclear weapons, including the possibility of a nuclear winter.

Joseph Rotblat and the Pugwash Conferences on Science and World Affairs: The 1995 prize was shared by Mr. Rotblat, a scientist who withdrew from efforts by the United States and Britain during World War II to produce nuclear weapons, and by the Pugwash Conferences, a lobby group built on a 1955 manifesto by Albert Einstein and Bertrand Russell on the dangers of nuclear war.

International Atomic Energy Agency: The group, which seeks to control the use of nuclear weapons, and its director general at the time, Mohamed ElBaradei, received the 2005 award “for their efforts to prevent nuclear energy from being used for military purposes and to ensure that nuclear energy for peaceful purposes is used in the safest possible way.”

International Campaign to Abolish Nuclear Weapons: This group of nongovernmental organizations puts pressure on governments to enforce the 1970 Treaty on the Non-Proliferation of Nuclear Weapons and received the 2017 award “for its work to draw attention to the catastrophic humanitarian consequences of any use of nuclear weapons.”

President Barack Obama: When the U.S. leader received the award in 2009, the committee noted that “emphasis was also given to his support — in word and deed — for the vision of a world free from nuclear weapons.”

But the committee’s decision follows intermittent threats by President Vladimir V. Putin of Russia about using tactical nuclear weapons in Ukraine, and after he said last month that he would lower the threshold for his country’s use of those weapons. American and NATO officials have said that they have detected no preparations by Russia for their use but have sought to make clear to the Kremlin that the Western alliance, too, was prepared to use its nuclear weapons if necessary.

Just before the Nobel was announced, NATO declared that its annual nuclear exercise called “Steadfast Noon” would begin on Monday, involving 60 aircraft and 2,000 military personnel in Western Europe. A senior Biden administration official said in June that the United States may be forced to expand its nuclear arsenal because of threats from Russia and China.

And the United States is already in the midst of a decades-long modernization program for its nuclear arsenal that has been estimated to cost some $1.7 trillion.

“The nuclear powers are modernizing and upgrading their arsenals,” the Nobel committee said in announcing Friday’s prize. “New countries appear to be preparing to acquire nuclear weapons; and threats are being made to use nuclear weapons in ongoing warfare. At this moment in human history, it is worth reminding ourselves what nuclear weapons are: the most destructive weapons the world has ever seen.”

China is rapidly expanding its nuclear arsenal, while forming a stronger alliance with Russia, which has high-level nuclear technology. Mr. Putin has boasted that Russia’s next-generation hypersonic missiles — which have shown mixed results in recent testing — can deliver nuclear warheads to any point on the globe, evading any air defenses.

Both Russia and China are increasingly allied to Iran, which is considered perhaps a year away from being able to create a nuclear warhead to fit to a missile.

There are concerns that Russia might be willing to provide Tehran with nuclear technology in return for Iran’s continued support for Moscow’s war in Ukraine. Iran is already believed to have supplied sophisticated drones and short-range ballistic missiles to Russia.

North Korea is also part of the informal group of countries at odds with an American-led order, and it has an active nuclear-weapons program and increasingly sophisticated missiles.

But many analysts and officials believe that the most urgent risk stems from the war in Ukraine, where one nuclear superpower, the United States, is sending sophisticated weapons to back the country’s defense against the world’s other nuclear superpower, Russia.

When Russia was struggling earlier in the war, in the fall of 2022, U.S. officials reportedly believed there was an even chance that Mr. Putin might authorize nuclear weapons to be used in certain circumstances.

In a speech at the time, Mr. Putin raised the specter of renewed nuclear weapons use by referring to America’s bombing in World War II.

“The United States is the only country in the world to have used nuclear weapons twice, destroying the Japanese cities of Hiroshima and Nagasaki,” Mr. Putin said. “By the way, they set a precedent.”

It was a suggestion that Mr. Putin’s takeaway from the atomic bombs of 1945 was very different from that of the Nobel committee and the organization it honored on Friday. Rather than set a taboo for using nuclear weapons, Mr. Putin was suggesting, those bombings had opened the door to such weapons being used again.

The threat of Russia using nuclear weapons at the time was considered real enough that strong messages were passed to Moscow, by official channels and in person, by the C.I.A. director, William Burns, about the consequences.

Now, Western officials and analysts generally believe that Mr. Putin will not use nuclear weapons so long as his forces are making progress on the front line. They note that, were he to deploy such weapons, he could face backlash from key Russian partners like China, and that the battlefield advantage of using those weapons is not clear.

But the Kremlin has sought to keep the threat alive, especially as European leaders and the White House consider Ukraine’s urgent request to use long-range missiles provided by the West against targets deep inside Russian territory. Mr. Putin said last month that such a move would put his country “at war with NATO.”

And to further drive home the point, Mr. Putin announced later last month that Russia would adjust its doctrine defining when the country could use nuclear weapons. He said that Russia would treat “aggression against Russia by any nonnuclear state, but with the participation or support of a nuclear state” as a “joint attack on the Russian Federation.”

The Kremlin said the new language was meant as a “signal” warning Ukraine’s backers “about the consequences in the case of their participation in an attack on our country by various means.”

Any eligible nominator can put forward a candidate, and sometimes those nominees are contentious and not seriously considered. Many candidates are nominated numerous times.

Nominators include academics, such as university rectors and chancellors, and professors of political and social science, history, philosophy, law and theology. Leaders of peace research institutes and institutes of foreign affairs can also nominate potential recipients, as can members of national assemblies, governments and international courts of law.

Others who can make nominations include previous Peace Prize laureates, board members of organizations and institutions that have received the award, present and past members of the Norwegian Nobel Committee, and former advisers of the Norwegian Nobel Institute.

There are few criteria for who can be nominated, but the selection process is a rigorous one that plays out over months, according to the Norwegian Nobel Committee. Secret deliberations begin in February, and the committee narrows the list to 20 to 30 candidates before conducting months of research.

The committee then makes its decision through a simple majority vote in October before announcing the laureate’s name. A ceremony is then held in December in Oslo, where the recipient delivers a lecture and receives the Nobel Prize medal, diploma and monetary award.

Japan recognized about 650,000 survivors in the wake of the war, but as the decades pass, the number still living has dwindled, and many of those who remain are now in their 80s. About 114,000 are still alive, according to Nihon Hidankyo, the grass-roots organization that received the Nobel Peace Prize on Friday.

Many of the survivors have dedicated their lives to recounting their stories of loss and excruciating physical and emotional injury. Their powerful testimony has contributed to a broader understanding of the profound devastation of nuclear war. This year, The New York Times’s Opinion section wrote about the survivors.

Nihon Hidankyo, established 11 years after the end of World War II, began as an organization representing the survivors of the atomic bomb who continued to suffer not only the physical effects of radiation but also the social stigma associated with the war.

Nihon Hidankyo is the only nationwide group of those survivors in Japan, with members in all of the country’s 47 prefectures. In the decades since its founding, the group has sent survivors around the world to share their experiences of living with the effects of radiation exposure from an atomic bomb.

“Humanity must never again inflict nor suffer the sacrifice and torture we have experienced,” the group said in its founding statement in 1956.

During the ceremony for the 2005 Peace Prize — given to the International Atomic Energy Agency, which monitors nuclear capabilities and reports to the United Nations — the Nobel committee also mentioned Nihon Hidankyo and the hibakusha for their work in campaigning against nuclear warfare.

Here is a quick guide to this year’s prizes.

What are the Nobel Prizes?

Six Nobel Prizes are awarded every year, each recognizing an individual’s or organization’s groundbreaking contribution in a specific field. Prizes are given for physiology or medicine, physics, chemistry, economic science, literature and peace work, which often draws the most attention because of the fame of the people and groups nominated.

This year, there are 286 candidates for the Nobel Peace Prize — 197 individuals and 89 organizations, the Nobel committee said. Last year, the institute received more than 350 nominations. The highest number ever received was 376 candidates, in 2016. (Here’s how those nominations work.)

Previous Nobel Peace Prize recipients include Kailash Satyarthi and Malala Yousafzai (2014); President Barack Obama (2009); Nelson Mandela and F.W. de Klerk (1993); the 14th Dalai Lama, Tenzin Gyatso (1989); and Mother Teresa (1979).

When are the awards announced?

One prize is announced each day from Oct. 7 to Oct. 11, with one more on Oct. 14, between 5 a.m. and 7 a.m. Eastern. Announcements are mainly made from Oslo and Stockholm, and are streamed live on the official digital channels of the Nobel Prize organization.

The award for physiology or medicine was awarded on Monday to Victor Ambros and Gary Ruvkun for their discovery of microRNA and its role in post-transcriptional gene regulation.

The award for physics was awarded on Tuesday to John J. Hopfield and Geoffrey E. Hinton for discoveries that helped computers learn more in the way the human brain does, providing the building blocks for developments in artificial intelligence.

The award for chemistry was awarded on Wednesday to three scientists for predicting and creating proteins. The laureates are Demis Hassabis and John Jumper of Google DeepMind, who used A.I. to predict the structure of millions of proteins; and David Baker at the University of Washington, who used computer software to invent a new protein.

The award for literature was awarded on Thursday to Han Kang, the South Korean author best known for the novel “The Vegetarian.” Ms. Han was recognized for “intense poetic prose that confronts historical traumas and exposes the fragility of human life,” said Mats Malm, the permanent secretary of the Swedish Academy.

The award for peace work was awarded on Friday to the Japanese organization Nihon Hidankyo, a grass-roots movement of atomic bomb survivors, for working toward a world free of nuclear weapons.

The award for economic sciences will be announced on Monday.

What do the laureates receive?

Nobel Prize laureates receive a diploma, a medal and a document detailing the Nobel Prize amount, which this year is set to be 11 million Swedish kronor or about $1.07 million in current exchange rates.

Who were last year’s recipients?

The award for peace work went to Narges Mohammadi, a jailed Iranian activist, “for her fight against the oppression of women in Iran and her fight to promote human rights and freedom for all.”

Among the notable laureates last year was the Norwegian author Jon Fosse, who was awarded the Nobel Prize for Literature “for his innovative plays and prose which give voice to the unsayable.” Some of his most important works include the seven novels in his “Septology” series and “Morning and Evening.”

Katalin Karikó and Drew Weissman were awarded the Nobel Prize in Physiology or Medicine for their discoveries that led to the development of effective vaccines against Covid-19.

See a complete list of 2023 winners here.